Cabbage leaves being eaten

The only way to prevent this is to use some kind of netting. If you can make up a frame of rounded hoops of heavy steel wire with chicken wire netting over it, these can be made in sections of about one metre wide and moved into position as needed, and last for many years.

The problem is lessened when cabbage grows taller, as the pigeons do not like to have anything obscure their line of sight, but in winter they will risk it and land on the cabbages to feed.